Shonai Takaharu, Carpenter Jeffrey S, Lemieux Susan K, Harada Kuniaki, Omori Kazumi, Kaneko Nobuaki, Fukushima Takanori
Department of Radiology, West Virginia University Hospital, Morgantown, West Virginia, USA.
J Magn Reson Imaging. 2008 Jun;27(6):1362-70. doi: 10.1002/jmri.21371.
To improve vessel visibility in time-of-flight MR angiography (TOF-MRA) by careful consideration of coil choice, coil position, and frequency offset and profile of the nonspatially selective chemical shift selective (CHESS) presaturation pulse.
The effects of both the CHESS and the excitation radiofrequency (RF) pulses on flow signal and signals from stationary substances were evaluated by changing the spatial area where RF pulses were applied to upstream flow in a flow phantom and in human subjects. The difference between the eight-channel phased-array receive-only coil and the transmit-receive coil was evaluated.
The CHESS pulse suppresses the flow signal over a wider frequency range than the signals from stationary substances, especially when using the body coil for transmission. Even without presaturation pulse, the excitation pulse slightly suppressed the flow signal. Adjusting the position of the transmit-receive coil relative to the head improved these TOF-MRA images. The results were better than those obtained with the eight-channel coil.
The excitation and the nonspatially selective CHESS pulses degraded the flow signal. Our results suggest that reduced spatial extent of RF pulse application to upstream flow can improve image quality of TOF-MRA. This result can be implemented on conventional scanners.
通过仔细考虑线圈选择、线圈位置以及非空间选择性化学位移选择（CHESS）预饱和脉冲的频率偏移和轮廓，提高飞行时间磁共振血管造影（TOF-MRA）中的血管可视性。
通过改变在流动模型和人体受试者中射频脉冲应用于上游血流的空间区域，评估CHESS脉冲和激发射频（RF）脉冲对血流信号和静止物质信号的影响。评估了八通道相控阵仅接收线圈和发射-接收线圈之间的差异。
CHESS脉冲在比静止物质信号更宽的频率范围内抑制血流信号，尤其是在使用体线圈进行发射时。即使没有预饱和脉冲，激发脉冲也会轻微抑制血流信号。调整发射-接收线圈相对于头部的位置可改善这些TOF-MRA图像。结果优于使用八通道线圈获得的结果。
激发脉冲和非空间选择性CHESS脉冲会降低血流信号。我们的结果表明，减少射频脉冲应用于上游血流的空间范围可提高TOF-MRA的图像质量。这一结果可在传统扫描仪上实现。
